What problem was under investigation?
The Washington State Department of Health investigated the occurrence and possible risk factors for neural tube defects in Yakima, Benton, and Franklin counties. Neural tube defects are major birth defects of a baby's brain and spine, including anencephaly and spina bifida. These conditions occur early in pregnancy, often before a woman realizes she's pregnant. Spina bifida can cause physical and cognitive disabilities that range from mild to severe depending on the degree that the spinal cord is affected. Anencephaly, the condition we were focusing on, is always fatal. Many infants are stillborn or die within hours or days after delivery.
Why was the investigation started?
A health care provider in central Washington reported an unusual number of infants born with anencephaly. After verifying this concern through hospital records, we partnered with local public health authorities and the Centers for Disease Control and Prevention (CDC) on an investigation into neural tube defects including spina bifida and anencephaly in the area.
What did you look at during the initial investigation?
We compared information from prenatal records and hospital records of women who had a pregnancy affected by a neural tube defect and women with pregnancies not affected by birth defects during the same time period. We looked at several risk factors for neural tube defects including, but not limited to, documentation of folic acid use (including prenatal vitamins), pre-pregnancy weight, family history of neural tube defects, and health risk behaviors of the mother during pregnancy. We also looked at the source of home drinking water.
What did you find?
We were not able to find any significant differences between women who had pregnancies affected by a neural tube defect and those with unaffected pregnancies. We did note that all women in the investigation had low early pregnancy folic acid use. So, we used other data we collect on recently pregnant women statewide to explore this further. We compared early pregnancy folic acid use in this three-county area with the rest of the state. For 2009-2011, about 61 percent of survey respondents in the three-county area – compared with about 50 percent of respondents from the rest of Washington – did not take a multivitamin, prenatal vitamin, or folic acid vitamin at all in the month before they got pregnant.
Is it common not to find answers?
Unfortunately, in these types of investigations it is common to find no particular risk factor that stands out as a likely explanation for a high rate. Even though the rate of neural tube defects in the three-county area is higher than average, the total number of cases is small in terms of numbers typically needed to identify causes of these birth defects.
What happened next?
Although we did not find any significant differences, we were still concerned about the high rate of anencephaly in the area. We held listening sessions with the affected communities to share our findings to date and learn about community concerns. In 2014, we convened a Neural Tube Defect Cluster Advisory Committee to help identify actions to prevent or reduce neural tube defects in the area, to improve reporting of neural tube defects, and to provide advice about additional investigation to assess potential exposures. We shared our initial findings and community concerns with the Advisory Committee and they assisted in the development of an action plan. The Advisory Committee recommended we continue to monitor neural tube defects in the three-county area, that we interview mothers to identify any common exposures, and that we conduct prevention activities. We followed the action plan and reported to the Advisory Committee regularly. In December 2016, the Advisory Committee recommended we write up our findings, discontinue the investigation, continue enhanced surveillance in the three-county area for at least one more year, and focus on activities to promote the use of folic acid by all women of reproductive age. In September 2017, we issued a report on the investigation which is posted here. In January 2018, the Department of Health discontinued enhanced surveillance activities, reverting to statewide passive birth defects surveillance.
Should women who live in the three-county area who are pregnant or considering pregnancy be concerned?
While the rate of anencephaly in the three-county area is higher than the national rate, the risk of having a baby with anencephaly is still quite low. About one in every 1,000 live births in the area is affected by anencephaly.
How can neural tube defects be prevented?
The most important way to prevent these birth defects is taking vitamins containing folic acid and eating foods high in folate or folic acid. Some foods, like leafy greens and citrus fruits, are naturally high in folate. Folic acid is also added to many breakfast cereals and other grain products labeled “enriched,” such as bread, pasta, and rice. Most experts recommend all women of reproductive age take a daily supplement containing 400 micrograms (mcg) of folic acid.
We also encourage women to talk to their health care provider about their health status, family history, and medication use to assess their individual risk and ways to further prevent neural tube defects. Read more about the recommended daily amounts of folic acid (CDC website).
Avoiding some medications while pregnant can reduce the likelihood of neural tube disorders. Women should check with their health care provider for guidance on medication safety during pregnancy.
Avoiding drinking water with high levels of nitrates may also reduce reproductive risks. Our nitrate information page, as well as information on the CDC and the Environmental Protection Agency (EPA) websites, notes that high nitrate levels in drinking water may increase the risk of miscarriage or certain birth defects. Women on private well water who are pregnant or planning pregnancy should have their water tested for nitrates and avoid drinking it if levels are higher than 10 mg/L.
I'm pregnant, what should I do to make sure my baby doesn't develop a neural tube defect?
Women who are pregnant or planning to become pregnant should follow their health care provider's advice regarding diet, medications, and other health issues including taking vitamins containing folic acid.
Do you think that radiation exposure from Fukushima may be a potential cause of this increased rate?
Because the elevated rate of cases existed long before the Fukushima event and continued after it is not likely Fukushima has any link to the rates of anencephaly in the area.
Do you think that radiation exposure from Hanford Nuclear Facility may be a potential cause of this increased rate?
For radiation from Hanford to be a potential cause of the elevated rates over several years and across the three-county area, there must be a way that several of the women could have been exposed to radiation from Hanford. As part of our investigation, we consulted with radiation experts at the Department of Health to consider potential ways people in the three-county area could be exposed to radiation from Hanford. This includes considering exposures to air, water, soil, agricultural products, and occupation to see if any of these were possible sources of radiation exposure.
Our role as the State Department of Health is to examine the work of federal contractors and to verify the ongoing monitoring tests they conduct to ensure workers and surrounding communities are not being exposed to radiation releases. There are reports of extensive monitoring of samples of air, surface water, river water, groundwater, soil, river sediment, agricultural crops, and animal and plant life going back to 1959. In addition to environmental samples, these reports also discuss measurements of radiation that may be traveling through the air after being emitted from radioactive material. These reports indicate that radionuclide concentrations at the site perimeter and offsite are mostly similar to concentrations of naturally occurring radiation and radiation from fallout of historical atmospheric testing of nuclear weapons (together these are referred to as background radiation) or the concentrations are too low for laboratory instruments to detect.
We considered drinking water from the Columbia River as a potential source of radiation exposure. However, decades of tests at the Richland drinking water intake have found concentrations of radionuclides are indistinguishable from background. Furthermore, our investigation revealed none of the women with neural tube defect-affected pregnancies lived in residences served by water systems that get their water from the Columbia River.
There have been periodic radiation releases from the Hanford site, but the vast majority have gone into the ground on the site itself, and to a lesser degree into the Columbia River. Most of the releases to the river happened decades ago, and radioactive contaminants have long since been diluted, flowed downstream into the ocean or are trapped in sediment behind the dams on the Columbia River. Some of the releases to the ground have migrated into groundwater beneath Hanford, and are slowly leaking into the river, but as noted above, tests find river concentrations are diluted quickly and are indistinguishable from background at Richland drinking water intake. Most of the releases into air also happened decades ago. While substantial quantities of radioactivity were released, most involved very short lived radionuclides, which have long since decayed away.
The women with neural tube affected pregnancies lived throughout the three-county area and the distribution of cases is similar to the population distribution. There were more cases in the population centers (city of Yakima, lower Yakima Valley and the Tri-Cities area of Richland, Kennewick and Pasco). Residences in the city of Yakima and the lower Yakima Valley are generally upwind of the prevailing southwest to northeast winds around the Hanford site. The results of decades of environmental sampling together with the investigation of drinking water sources do not identify a common source of exposure to radiation from Hanford. For this reason, we conclude that it is unlikely that Hanford radiation exposures explain the overall increase in the neural tube defect rate in this area.
Could these cases be caused by exposure to pesticides?
Pesticide exposure is difficult to determine because of the vast number of pesticide products and the difficulty of learning whether people were exposed. We considered three different approaches to look at pesticide exposure. We explored regional exposure to pesticides known to be associated with neural tube defects, the residential proximity of the women with impacted pregnancies to agricultural areas, and parental occupation. We did not find a higher potential for pesticide exposure among women with affected pregnancies compared to other pregnancies in the three-county area. We did not find evidence for higher exposure to pesticides associated with neural tube defects. We did not find mothers of affected pregnancies lived closer to agricultural fields than mothers of unaffected pregnancies, and we did not find that mothers or fathers of neural tube defect affected pregnancies were more likely to have an occupation associated with pesticide use. We also saw no seasonality among the anencephaly-affected pregnancies. Nonetheless, we cannot rule out the possibility that pesticide use might be contributing to the increase in anencephaly-affected pregnancies in the three-county area, because we were not able to examine all possible types and sources of pesticide exposure.
Could these cases be caused by nitrates or bacteria in drinking water?
A possible link between anencephaly and bacterial or nitrate levels in drinking water is unlikely. We looked at the residential water source to see if the affected pregnancies were on public water systems or private wells. Most women with affected and unaffected pregnancies lived in homes served by large public water systems. We reviewed the nitrate levels in the public water systems serving the cases' homes during the investigation period. Nitrate levels in these public water systems did not exceed federal drinking water safety standards of 10 mg/L and only rarely exceeded 5mg/L. These public water systems are tested at least annually for nitrate and monthly for bacteria to ensure they remain within acceptable limits.